basic principals of inrush current limiting

of 20 /20
EPCOS AG A Group Company of TDK-EPC Corporation PPD • PD VAR PM Munich, Germany Feb 2010 Protection Devices Inrush Current Limiting NTCs

Author: chandan-vaishnav

Post on 10-Mar-2015

49 views

Category:

Documents


4 download

Embed Size (px)

TRANSCRIPT

Protection DevicesInrush Current Limiting NTCs

EPCOS AG A Group Company of TDK-EPC Corporation PPD PD VAR PM Munich, Germany Feb 2010

Protection devicesMajor applications Overload protection Telecom line protection Surge voltage protection at Telecom installations and AC lines PTC relays for compressors start LED current regulation Heating elements Surge arresters PTC elements Disk varistors ICLs Inrush current limiting

Protection Devices: ICL Basis

TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 2

ICLs - The Safe Start

Inrush Current Limiters from EPCOS. A safe and reliable protection for capacitive loads in switching circuits and for soft starting of inductive loads. TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 3

Protection Devices: ICL Basis

Principle of ICL-NTCs

R

TResistance / Temperature Curve Typical load current characteristic

Protection Devices: ICL Basis

TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 4

ICL - Inrush Current LimitingReducing of inrush current in order ... Inrush Current Limiting in

to reduce the peaks in the circuit to protect other components to avoid tripping of fuses to reduce PCB size compared to fixed resistors

Switched Mode Power Supplies Soft Start of Electric Motors Halogen Lamps Fluorescent Lamps Transformers

Protection Devices: ICL Basis

TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 5

ICL Advantages Wide product range 12 various ceramic systems Rated resistance(25 : 1 up to 80 [ohm] C) Max. permissible current : 1.3 up to 20.0 [A] No current derating in the range of 0 to 65 C (except S237) High reliability Tested according to IEC 60068 (dry heat, damp heat, rapid temperature cycling) Endurance, pulse strength are proved. UL approval (E69802) Inside- and outside kink lead are also available (Inline kink lead is standard.)

Protection Devices: ICL Basis

TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 6

ICL Product FamiliesSeries B57153S B57235S B57236S B57237S B57238S B57364S B57464S 0.1 1.0 10.0 100.0 Ohm

Protection Devices: ICL Basis

TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 7

ICLs: Structure and PrincipleR

TR/T characteristics of a NTC

Sintering various oxide together with other additives produces a polycrystalline, semi-conductive, temperature depending ceramic. This phenomenon results in a Negative Coefficient Thermistor (NTC)

Protection Devices: ICL Basis

TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 8

Circuit PrincipleThe ICL is placed in series with the load before the capacitive or inductive load. The NTC thermistors specifically developed for this application limit the current at turn-on by their relatively high cold resistance. As a result of the current load the thermistor heats up and reduces its resistance. Hence the ICL provides protection from undesirable high inrush currents but features low power consumption during continuous operation.Protection Devices: ICL Basis TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 9

Principle of ICL-NTCs

The thermal properties of a Power NTC can be used to limit harmful switch-on currents of capacitive loads. At turn-on the NTC restricts the current flow into the capacitor due to its `cold` resistance. The current flowing through the NTC causes it to self heat and thereby reducing its resistance by a factor 10 to 50.

Protection Devices: ICL Basis

TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 10

Load Derating of ICLs

Derating curve for maximum permissible continuous current vs ambient temperature

Protection Devices: ICL Basis

TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 11

Circuit Examples

Typical Power Supply (Line Line)Input protected by Varistor against over-voltages. Capacitor protected against inrush-currents by an ICL. Load fuse additionally used to protect the Varistor against thermal runaway.

~

Varistor ICLProtection Devices: ICL Basis TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 13

Power Supply with Relay (Line-Line)Sensing circuit shorts-out the ICL when the capacitor has reached a predetermined voltage i.e. 95% of charge..

~Varistor ICLProtection Devices: ICL Basis TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 14

Protection of Drives and Invertors

Mains

Rectifier

Inverter

Motor M

DC-Link

Block Varistors protect each phase of Drive ICLs protect the Capacitors

Protection Devices: ICL Basis

TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 15

Fields of Application

Disks in Entertainment ElectronicsA guideline for the selection of types for this application.

VAR

ICL

S05 S20, ETFV, SFS 175V / 275V S153, S236, S237 4.7 / 10.0 Ohm

Protection Devices: ICL Basis

TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 17

Disks in Consumer Electronics

A guideline for the selection of types for this application.

VAR ICL

S05 S20, 275V / 300V S153 S364

Protection Devices: ICL Basis

TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 18

Disks in Power Supplies

SMPS / UMPS

Compressor

Energy-Meter

Varistors S++K175 / 275 (E2) SFS; ETFV ICL S153; S235;S236Protection Devices: ICL Basis

Varistors S++K175 - 420 (E2) SFS; ETFV ICL S153;S235;S236

Varistors S10K385 / 420 / 510 (E2) S14K385 / 420 / 510 (E2) S20K385 / 420 / 510 (E2)

TDK-EPC Corporation 2010 PPD PD VAR PM 01/10 19

www.tdk.co.jp www.epcos.com